The conventional smooth bore shotgun and similar multiple projectile weaponry disperses shot in a pattern that diverges rapidly after it has left the muzzle. This characteristic fan out increases the probability of a hit at short range but limits the weapon's effectiveness as the distance to target increases. At a distance of only 40 yards, for example, lead shot fired from a conventional 12 gauge shotgun will typically deliver only 40 percent of the shot inside a 30 inch circle. This reduced pellet density can shorten the effective range of the shotgun to about 20 yards.
In order to tighten the shot pattern and extend the effective range of a shotgun, the barrel may be constricted or “choked” at or near the muzzle end. The constriction can range from as little as 0.005 inches for skeet shooting, to about 0.050 inches for shooting at more distant targets. While the barrel itself is often designed to have some built-in choke, detachable and interchangeable “choke tubes” of varying constrictions are commonly used to adapt the conventional shotgun for use in a variety of different shooting scenarios.
Although traditional choke tubes and choked barrels can reduce shot pattern spread there is a limit to the amount of shot pattern control that a conventional choke tube can provide and there is a high degree of pattern variability and density from shot to shot. The large number of shotgun choke systems that have been developed over the years demonstrates the difficulty of the problem.
Recently, choke tubes and choke systems that retard the shot wad before it exits the muzzle have been introduced in an effort to prevent the wad and turbulent gas behind from interfering with the shot in the instant after the shot exits the muzzle. For example, U.S. Pat. No. 5,452,535, issued Sep. 26, 1995 to See et al. (“'535 patent”), discloses wad retardation devices that employ radial projections such as ridges, pins, studs, or set screws, or an applied grit that extend inwardly around an inner circumference of a barrel in order to retard the velocity of the wad before it exits the muzzle. Interference with the shot trajectory and pattern by the wad and gas turbulence downstream of a shotgun muzzle may thus be inhibited. U.S. Pat. No. 6,128,846, issued on Oct. 10, 2000, of which an applicant hereunder is named a co-inventor, discusses improvements to the devices discussed in the '535 patent.
Devices manufactured according to the '535 and '846 patents demonstrably improve shotgun shot pattern consistency and predictability. However, improvements in shot pattern control methods and devices are still needed. For example, the radial projections needed by such devices must be machined to very close tolerances which can add significantly to the cost of manufacture. Moreover, the projections are positioned directly in the path of the accelerating shot and wad and are thus subjected to wear every time the gun is fired and will eventually become worn to the point that they are no longer effective. The use of “hard” shot materials such as bismuth, steel, tungsten-iron, tungsten-nickel-iron and tungsten polymer exacerbates the problem. Thus, it would be advantageous to provide a system that effectively retards the wad and thereby inhibits shot interference and shot pattern distortion from the wad and gas turbulence downstream of a shotgun muzzle without employing radial projections such as ridges, pins, studs, screws, grit or abrasives. Of course, any such system should also achieve consistent, predictable and focused shot patterns, be adaptable to a variety of shot spreads for long and short range shooting scenarios, and at the same time be safe, durable and easy to use. Embodiments according to the present invention are directed to addressing the foregoing needs.